High pressure feeder and method of operating to feed granular or fine materials

Abstract

A coal feed system to feed pulverized low rank coals containing up to 25 wt % moisture to gasifiers operating up to 1000 psig pressure is described. The system includes gas distributor and collector gas permeable pipes imbedded in the lock vessel. Different methods of operation of the feed system are disclosed to minimize feed problems associated with bridging and packing of the pulverized coal. The method of maintaining the feed system and feeder device exit pressures using gas addition or extraction with the pressure control device is also described.

What is claimed is: 
     
       1. A method of using a coal feeder system comprising a coal surge bin configured to store processed coal for feeding into a gasifier; a lock vessel coupled to the coal surge bin, the lock vessel being a pressure swing device; a gas collector and distributor disposed within the lock vessel, the gas collector and distributor configured to distribute gas within the lock vessel; a gas permeable membrane disposed within a conical section of the lock vessel; a feed vessel coupled to the lock vessel, the feed vessel configured to operate at a substantially constant pressure; a pressure control device programmed to maintain a substantially constant pressure between the feed vessel and a gasifier; and a feeder device configured to control a coal feed rate into the gasifier, the method comprising the steps of:
 loading the lock vessel with pulverized coal; 
 pressurizing the lock vessel by a slow pressurization step for up to about sixty seconds; 
 pressurizing the lock vessel by a fast pressurization step till the pressure is within about 5% of a final desired pressure; and 
 pressurizing the lock vessel by a slow pressurization step until a final desired pressure is reached. 
 
     
     
       2. A method of using a coal feeder system comprising a coal surge bin configured to store processed coal for feeding into a gasifier; a lock vessel coupled to the coal surge bin, the lock vessel being a pressure swing device; a gas collector and distributor disposed within the lock vessel, the gas collector and distributor configured to distribute gas within the lock vessel; a gas permeable membrane disposed within a conical section of the lock vessel; a feed vessel coupled to the lock vessel, the feed vessel configured to operate at a substantially constant pressure; a pressure control device programmed to maintain a substantially constant pressure between the feed vessel and a gasifier; and a feeder device configured to control a coal feed rate into the gasifier, the method comprising the steps of:
 over-pressurizing the lock vessel before opening a first valve in a balance line; and 
 opening a second valve between the lock vessel and the feed vessel after a time delay. 
 
     
     
       3. The method of  claim 2 , wherein excess gas is released from the pressure control device and from gas collectors in the lock vessel such that a pressure in the feed vessel and the feeder device are maintained substantially constant. 
     
     
       4. A method of using a coal feeder system comprising a coal surge bin configured to store processed coal for feeding into a gasifier; a lock vessel coupled to the coal surge bin, the lock vessel being a pressure swing device; a gas collector and distributor disposed within the lock vessel, the gas collector and distributor configured to distribute gas within the lock vessel; a gas permeable membrane disposed within a conical section of the lock vessel; a feed vessel coupled to the lock vessel, the feed vessel configured to operate at a substantially constant pressure; a pressure control device programmed to maintain a substantially constant pressure between the feed vessel and a gasifier; and a feeder device configured to control a coal feed rate into the gasifier, the method comprising the steps of:
 under-pressurizing the lock vessel before opening a first valve between the lock vessel and the feed vessel; and 
 opening a second valve in the balance line after a time delay. 
 
     
     
       5. The method of  claim 4 , wherein additional gas is added to at least one of the feed vessel and a solids stream flowing through the pressure control device to maintain a substantially constant pressure in the feed vessel and the feeder device. 
     
     
       6. A method of using a coal feeder system comprising a coal surge bin configured to store processed coal for feeding into a gasifier; a lock vessel coupled to the coal surge bin, the lock vessel being a pressure swing device; a gas collector and distributor disposed within the lock vessel, the gas distributor configured to distribute gas within the lock vessel; a gas permeable membrane disposed within a conical section of the lock vessel; a feed vessel coupled to the lock vessel, the feed vessel configured to operate at a substantially constant pressure; a pressure control device programmed to maintain a substantially constant pressure between the feed vessel and a gasifier; and a feeder device configured to control a coal feed rate into the gasifier, the method comprising the steps of:
 over-pressurizing the lock vessel by about three to fifteen percent higher than the pressure in the feed vessel; and 
 releasing an entrained gas from the lock vessel through a plurality of vents to the surge bin until the lock vessel pressure is substantially equal to the feed vessel pressure. 
 
     
     
       7. The method of  claim 6 , further comprising the step of releasing an entrained gas substantially uniformly throughout the lock vessel to fluidize materials in the lock vessel. 
     
     
       8. The method of  claim 7 , further comprising steps of:
 venting the lock vessel from about one to three seconds during the fast pressurization step; and 
 releasing an entrained gas substantially uniformly throughout the lock vessel to fluidize materials in the lock vessel before the feed vessel pressure is reached. 
 
     
     
       9. The method of  claim 6 , further comprising the step of adding a gas to a conical section of the lock vessel while the gas is being released through a network of internal pipes coupled to a ring header.